Indoor tanning with lamps and beds boosts the risk of nonmelanoma skin cancer, especially among younger people, a meta-analysis suggested.

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Point out that in a subanalysis of patients younger than 25, indoor tanning was associated with a significantly higher relative risk for basal cell carcinoma and a higher but nonsignificant relative risk for squamous cell carcinoma.

Indoor tanning with lamps and beds boosts the risk of nonmelanoma skin cancer, especially among younger people, a meta-analysis suggested.

Patients who had ever used a form of indoor tanning had a significantly increased risk of basal (BCC) and squamous cell carcinoma (SCC) at relative risks of 1.67 and 1.29, respectively (95% CI 1.29 to 2.17 and 95% CI 1.08 to 1.53), according to Eleni Linos, MD, of the University of California San Francisco, and colleagues.

In a subanalysis of patients younger than 25, indoor tanning was associated with a significantly higher relative risk for BCC (RR 1.40, 95% CI 1.29 to 1.52) and a higher but nonsignificant relative risk for SCC (RR 2.02, 95% CI 0.70 to 5.86), Linos' group wrote online in BMJ.

"The temporal relation in which indoor tanning at a young age is a stronger risk factor not only supports a causal interpretation but also implies a critical period of higher susceptibility during early life," they said.

The incidence of BCC and SCC of the skin has increased substantially in the previous decades, but these diseases are frequently excluded from national cancer registries and cancer databases because they don't typically affect survival, the authors noted. Additionally, indoor tanning has linked with an increased risk of nonmelanoma skin cancer.

The researchers pooled data from 12 studies, which measured indoor tanning exposure of a combined 80,661 patients. They found a total 9,328 cases of BCC or SCC.

Linos and colleagues collected information on patients' age, sex, type of nonmelanoma skin cancer, type of study, statistical methods, and outcomes measured in each study, such as measures of dose exposure, ever use, or frequent use.

The researchers also performed subanalyses of patients younger than 25 and those who used frequent or high doses of indoor tanning.

Compared with participants who had never used indoor tanning, the population attributable risk was 3.7% for BCC and 8.2% for SCC, corresponding to a combined 170,652 cases of nonmelanoma skin cancer attributable to indoor tanning annually, they wrote.

The subanalysis in younger people also showed a 50% increased risk of BCC in patients who used high doses of indoor tanning, although the studies all used different definitions of "high dose," including 6 to 26 years of regular exposure and exposure more than five times per year (RR 1.50, 95% CI 0.81 to 2.77).

The authors said these associations suggest "a critical period for exposure during early life and a potential dose-response effect."

The study's main limitation was its reliance on data from observational and case-control studies. Also, the data came from studies conducted from the 1970s up to 2010, and indoor tanning devices changed over that time from high ultraviolet B output to ultraviolet A output. However, both "seem to be capable of causing significant mutagenic damage to skin," the authors stated.

In an accompanying editorial, Catherine Olsen, PhD, and Adele Green, PhD, of the Queensland Institute of Medical Research in Australia, noted that nonmelanoma skin cancers are less aggressive than malignant melanoma, but the treatment and costs associated with BCC and SCC are still substantial.

"Young people in particular should be made aware that the use of sunbeds for short-term cosmetic tanning carries the long-term price of an increased risk of skin cancer," they wrote.

A second commentary from Simon Nicholas Williams, PhD, of Northwestern University in Chicago, pointed out that a "tan tax" levied by the Obama administration in July 2010 seems to have reduced the use of indoor tanning facilities. He recommended that the European Union should consider a similar tax.

"It is estimated that the ["tan tax"] will raise $2.7 billion in revenue over a decade," he said. "All or a portion of this revenue could be earmarked for public health education initiatives warning of the dangers of ultraviolet radiation exposure."

The study was funded by awards from the NIH.

One co-author acted as a consultant for Genentech.

The commentary authors declared no conflicts of interest.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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